Magnetic field reversal of electric polarization and pressure-temperature-magnetic field magnetoelectric phase diagram of the hexaferrite Ba 0.4 Sr 1.6 Mg 2 Fe 12 O 22 .

Pressure, as an independent thermodynamic parameter, is an effective tool to obtain novel material system and exotic physical phenomena not accessible at ambient conditions, because it profoundly modifies the charge, orbital and spin state by reducing the interatomic distance in crystal structure. However, the studies of magnetoelectricity and multiferroicity are rarely extended to high pressure dimension due to properties measured inside the high pressure vessel being a challenge. Here we reported the temperature-magnetic field-pressure magnetoelectric (ME) phase diagram of Y type hexaferrite Ba 0.4 Sr 1.6 Mg 2 Fe 12 O 22 derived from static pyroelectric current measurement and dynamic magnetodielectric in diamond anvil cell and piston cylinder cell. We found that a new spin-driven ferroelectric phase emerged at P = 0.7 GPa and sequentially ME effect disappeared around P = 4.3 GPa. The external pressure may enhance easy plane anisotropy to destabilize the longitudinal conical magnetic structure with the suppression of ME coefficient. These results offer essential clues for the correlation between ME effect and magnetic structure evolution under high pressure.